Vitamin D Deficiency-Induced Proximal Myopathy in a Pediatric Patient During COVID-19 Lockdown: A Case Report.

Vitamin D deficiency is a significant public health concern that affects bone health and muscle function in children, especially in developing countries. The COVID-19 pandemic has intensified this issue because lockdowns have reduced sunlight exposure. We report a rare case of a 13-year-old Indian boy who developed severe proximal myopathy induced by vitamin D deficiency during the pandemic. The patient presented with generalized body aches, progressive lower limb weakness, difficulty walking, waddling gait, and a positive Gower's sign. Laboratory tests revealed severe hypovitaminosis D (25[OH]D level, 3.8 ng/ml), hypocalcemia, hypophosphatemia, elevated parathyroid hormone, and elevated alkaline phosphatase levels. Electromyography and nerve conduction study results were normal. The patient was diagnosed with vitamin D deficiency-induced proximal myopathy and osteomalacia, likely due to reduced sunlight exposure, inadequate dietary intake, and obesity. The treatment involved high-dose vitamin D supplementation, oral calcium, lifestyle modifications, and a structured physiotherapy program focusing on resistance training and functional mobility exercises. Despite biochemical normalization after 2 months, significant symptomatic improvement was achieved only after intensifying physiotherapy. By 7 months, the patient had fully recovered muscle strength, achieved normal gait, and maintained normal follow-up laboratory values. This case emphasizes the importance of considering vitamin D deficiency in children with muscle weakness during periods of limited sunlight exposure, and highlights the need for a multidisciplinary approach for effective management and full functional recovery.